Tagged Questions

Design of cryptographic protocols, i.e. ways of using algorithms (primitives) to achieve one or more security goals like integrity, confidentiality, authenticity (maybe together with non-security-related goals). If you ask about a specific protocol, tag with its name instead (or additionally, if ...

A more secure form of 'cookie' could be created for SSL communications through the following method.
The client generates and requests the server to sign a certificate.
Then the client authenticates ...

Assume:
$O$ be a reversible random permutation oracle on a finite set and $O^{-1}$ the inverse permutation (pretty much equivalent to a random permutation: What is the difference between a bijective ...

A client application needs to encrypt a UDP datagram for a server with known EC public key $P$. Performing a full ECDH key exchange would defeat the benefit of using UDP as a connectionless protocol. ...

As a social experiment (not a money-making scheme), I'm interested in developing a crazy cryptocurrency which, by its very design, will become worthless and untradable after a certain point. Ideally, ...

During a regular Diffie–Hellman public key exchange, Alice and Bob agree to use a prime number $p$ and a base $g$… which are both made public and are therefore also assumed to be known by Eve. Alice ...

I've recently been looking at how to do perfect forward secrecy on a unidirectional connection (server can only push messages to client, client cannot respond).
What I've come up with is the idea of ...

AES and DES are block ciphers. Mathematically, its the mapping from plaintext space to ciphertext space using the keys i.e. $\{{0,1}\}^k$ x $\{{0,1}\}^l \longrightarrow \{{0,1}\}^l$
I know that these ...

A digital currency system like Lucre (OpenTransaction) creates a coin by a mint blind signing the output of a hash function, which the payer then unblinds and pairs with the input to the has function.
...

I have a few requirements for a password reset system, along with some questions at the end as to its security.
Requirements
The aim is to provide a password reset mechanism satisfying the following ...

I am wondering if there are any links to articles or resources available online, or explanations that you can give, that would help me to understand the concept of a public key ring, and why I might ...

The Data Encryption Algorithm is designed to encipher and decipher blocks of data consisting of 64 bits under control of a 56-bit key.
If my data is more than 64 bits, (suppose 66 or 67 bits), will ...

In order to guard against denial-of-service attacks, I want to require clients to do some work (more work than the server does fulfilling the request) before talking to them.
Client connects
Server ...

I really don't know how to call this simple problem: Two (or more) parties need to establish a common (non-secret) value to be used as a seed for a deterministic RNG. The only requirement is that each ...

Let's suppose we have an Alice who knows a secret key A, and Bob who knows key B. Using their own keys, they each encrypt a message (Alice encrypts $m_A$, Bob encrypts $m_B$) with their own key, and ...

I am doing a research about secure communication protocols.
I would be interested to know whether a protocol exists such that it grants that the two end-points taking part to the communication cannot ...

Is this true that whenever you design a protocol using a hash function, you must prove its security under the random oracle?
I mean, is it possible to devise a protocol $P$ using a function $H$, and ...

I was playing around with a problem in e-voting schemes that use additive homomorphic encryption to tally votes, namely that at the end of the day somebody (or somebodies, if the secret material has ...

Let's say there are 100 choices (which are publicly known), each represented as a different string, and today you have to choose one of them. You need not reveal what that choice is right now, though. ...